Fabrication and characterization of α‑Fe₂O₃/Fe₃O₄ magnetic heterogeneous nanorods with PEG_2k as restricted growth agent

Abstract

For realizing the control of the preparation process for α-Fe₂O₃/Fe₃O₄ magnetic heterogeneous nanorods (MHNRs), the influence rules of key factors on the preparations of β-FeOOH nanorods (NRs) and α-Fe₂O₃/Fe₃O₄ MHNRs were revealed. Firstly, β-FeOOH nanorods (NRs) were fabricated with polyethylene glycol 2000 (PEG_2k) as the growth inhibitor in specific directions via the hydrolysis process, for smaller size, the fabrication conditions for β-FeOOH NRs including Fe³⁺ concentration, PEG_2k volume, hydrolytic temperature, and hydrolytic duration were optimized, and the optimal conditions were selected as 0.02 M of Fe³⁺, 0.20 g/L of PEG_2k, 80 °C of hydrolytic temperature, and 2 h of hydrolytic duration, the β-FeOOH NRs with average length and diameter of 199 nm and 55 nm were obtained. Secondly, α-Fe₂O₃/Fe₃O₄ magnetic heterogeneous nanorods (MHNRs) were prepared with PEG_2k as the reductant via the calcination-reduction process. For larger saturation magnetization (Ms) of α-Fe₂O₃/Fe₃O₄ MHNRs, the mass ratio of PEG_2k and β-FeOOH NRs, calcination temperature, and calcination time were investigated as were 3:1, 450 °C, and 2 h, respectively. And α-Fe₂O₃/Fe₃O₄ MHNRs with the average length of 229 nm, average diameter of 55 nm, and Ms of 81.3 emu/g were obtained. The novel and facile preparation process for α-Fe₂O₃/Fe₃O₄ MHNRs shortened the preparation period, omitted the reduction process using hydrogen enhancing the preparation security, and relized the controlled particle size and properties, there were not heavy metal elements in the nanosystem, laying the groundwork for the biomedical applications of α-Fe₂O₃/Fe₃O₄ MHNRs.

Graphical abstract

Highlights

• λ PEG2k was selected as the dispersant and reducing agent for α-Fe₂O₃/Fe₃O₄ MHNRs.

• λ A hydrolysis and calcination-reduction process for α-Fe₂O₃/Fe₃O₄ MHNRs was developed.

• λ The influence rules of factors on the precursors and α-Fe₂O₃/Fe₃O₄ MHNRs were revealed.

Introduction

Magnetic nanomaterials, especially magnetic nanorods (NRs), have garnered significant attentions due to their unique properties at the nanoscale [1, 2], which distinguish them from their bulk counterparts, and they exhibit enhanced magnetism, large surface area, and a variety of functional possibilities, making them promising for a wide range of applications across different fields [3, 4].

Considering biosafety and biocompatibility of magnetic nanomaterials in bio-medicine applications such as magnetic resonance imaging (MRI) [5], targeted drug delivery [6], hyperthermia therapy [7], and so on, iron oxide nanomaterials, especially Fe₃O₄ and α-Fe₂O₃, become the preferred magnetic nanomaterials [8]. However, the saturation magnetization (Ms) of Fe₃O₄ nanomaterials is large, which result in their agglomeration to the disadvantage of applications in bio-medicine; while, Ms of α-Fe₂O₃ nanomaterials is small, which is detrimental to the effects of magnetic field [9, 10]. For taking full advantage of magnetic field and avoiding the agglomeration of iron oxide nanomaterials, the α-Fe₂O₃/Fe₃O₄ magnetic heterogeneous nanomaterials (MHNMs) come into being [11, 12]. At the same time, many literatures have reported that nanorods can cross the cells’ membranes and enter into cells [13], therefore, the fabrication of α-Fe₂O₃/Fe₃O₄ magnetic heterogeneous nanorods (MHNRs) attracted more attentions.

To date, some of metods have been developed to prepare α-Fe₂O₃/Fe₃O₄ MHNMs [14], for example, the α-Fe₂O₃/Fe₃O₄ composites were prepared by H₂ annealing at 300 °C for 3 h [15], the α-Fe₂O₃/Fe₃O₄ nanocomposites were obtained via vacuum calcination process [16], and α-Fe₂O₃/Fe₃O₄ MHNMs via the caiciantion-reduction process [17, 18],

In this project, α-Fe₂O₃/Fe₃O₄ MHNRs were successfully prepared via the hydrolysis process and the calcination-reduction process with PEG_2k as the dispersant and reducing agent, and for better applications in bio-medicine, the preparation conditions for the precursor β-FeOOH nanorods (NRs) and α-Fe₂O₃/Fe₃O₄ MHNRs were optimized, and their controllable preparations were realized.

Experimental

Fabrication of β-FeOOH NRs and α-Fe₂O₃/Fe₃O₄ MHNRs

Various volumes (50–700 µL) of PEG_2k solution (1.0 kg/L) were taken into 100 mL double distilled water with magnetic stirring (600 rpm) for 10 min to form evenly distributed solutions (0.05–0.70 g/L) without pH adjustment for all the process. Differen masses (1.35 g, 2.7 g, 5.4 g, and 8.1 g) of ferric chloride hexahydrate, i.e. Fe³⁺ concetrations of 0.005 M, 0.01 M, 0.02 M, and 0.03 M, were severally added into the solutions in the requisite quantities, and the stirring (600 rpm) was continued for about 30 min until the two components were thoroughly blended. The homogeneous mixed solutions were transferred into the round bottom flasks, and the precursors of hydroxy-ferric oxide (β-FeOOH) were obtained after intense magnetic stirring (600 rpm) at the appropriate temperatures (75–95 °C) of the water bath for the corresponding hydrolytic durations (0.5–3.0 h). The obtained suspension was centrifuged under 10,000 rpm, and the solids were alternately washed for thrice with distilled water and absolute alcohol, the product was dried in oven of 60 °C for 12 h and ground, β-FeOOH NRs were obtained.

PEG_2k solids and 0.1 g of β-FeOOH NRs in different mass ratios of (2–7):1 were mixed evenly in crucibles. The crucibles were placed in the programmed temperature calciner at different temperatures (350–500 °C) for different times (0.5–5 h) with the heating rate of 3 °C/min. After calcination, naturely cooled to room temperature, ground, the α-Fe₂O₃/Fe₃O₄ MHNRs would be obtained.

Characterization of β-FeOOH NRs and α-Fe₂O₃/Fe₃O₄ MHNRs

The phase identifications of β-FeOOH NRs and α-Fe₂O₃/Fe₃O₄ MHNRs were characterized by Rigaku D/max 2500 PC X-ray diffraction (XRD) with Cu-Kα radiation, the morphologies and composition analyses were investigated with the scanning electron microscope (SEM, Thermo Fisher, QUANTA 250 FEG) and transmission electron microscopy (TEM, Hitachi, HT-7800) techniques, the magnetic measurements were taken on an ADE DMS-HF-4 vibrating sample magnetometer (VSM) equipment. The optimum experimental conditions for preparing the ideal nanorods were determined.

Results and discussion

Characteristics of β-FeOOH NRs

The SEM morphology, XRD pattern, and the statistics for the lengthes and diameters of β-FeOOH nanomaterials fabricated at hydrolytic temperature of 80 °C for 2.0 h with 0.20 M FeCl₃·6H₂O and 0.20 g/L PEG_2k were displayed in Fig. 1. Obviously, the β-FeOOH nanomaterials revealed the uniform nanorod structure as Fig. 1A, their statistics distributions for their lengthes and diameters followed a normal distribution as shown in Fig. 1C and D, their average length and diameter were approximately 199 nm and 55 nm, respectively. Figure 1B revealed the XRD pattern of the nanorods, their diffraction peaks at 26.8°, 34.2°, 35.3°, 39.4°, 46.6°, 56.2°, and 64.7° corresponded to the standard PDF card of β-FeOOH (JCPDS. 00-075-1594), respectively. Which certified the successful fabrication of β-FeOOH NRs [19].

Fig. 1.

SEM morphology (A), XRD pattern (B), and the distributions for their lengthes (C) and diameters (D) of β-FeOOH NRs fabricated at hydrolytic temperature of 80 °C for 2.0 h with 0.20 M FeCl₃·6H₂O and 0.20 g/L PEG_2k

Effects of different conditions on the morphology of β-FeOOH NRs

Figure 2A–D showed the SEM images of β-FeOOH NRs at 80 °C for 2.0 h with 0.50 g/L of PEG_2k and various concentrations of Fe³⁺ ion, revealing corresponding distinct sizes and diameters of β-FeOOH NRs as Fig. 2E. As the Fe³⁺ concentration increased, there was a higher propensity for crystal nucleus formation and increased polymerization between these nuclei, resulting in a direct augmentation of nanorod size and diameter during the crystal growth process. Notably, with Fe³⁺ concentration of 0.02 M, the β-FeOOH NRs exhibited comparatively smaller average dimensions of 211 nm in size and 57 nm in diameter. This unexpected outcome might be attributed to the role of PEG_2k as the dispersant, which possessed the capability to complex with Fe³⁺ ions, thereby yielding the observed results. These dimensions aligned precisely with requirements, prompting the selection of 0.02 M Fe³⁺ concentration for subsequent investigations.

Fig. 2.

SEM morphologies A–D of β-FeOOH NRs fabricated at hydrolytic temperature of 80 °C for 2.0 h with PEG_2k of 0.50 g/L and ferric trichloride of 0.05 M, 0.10 M, 0.20 M, 0.30 M, and their corresponding average lengthes and diameters E based on sample quantity of n ≥ 100

The influence of PEG_2k concentration in solution was subsequently investigated, and the SEM morphologies of β-FeOOH NRs fabricated at 80 °C for 2.0 h with ferric trichloride of 0.20 M and different PEG2k concentrations of 0.05 g/L, 0.10 g/L, 0.20 g/L, 0.30 g/L, 0.40 g/L, 0.50 g/L, 0.60 g/L, and 0.70 g/L, and their corresponding average lengthes and diameters were displayed as Fig. 3. Obviously, the fabricated β-FeOOH nanomaterials maintained the rod-like structure despite variations in PEG_2k concentration. Acting as the dispersant, PEG_2k facilitated the dispersion of iron ions, resulting in the formation of more uniform and smaller nanorods. Notably, lower PEG_2k concentration corresponded to longer nanorods, while the increase of PEG_2k concentration led to a gradual reduction in nanorod length, aligning with expectations that higher PEG_2k content enhanced dispersion, thus yielding shorter nanorods. However, upon 0.60 g/L of PEG_2k, the length of the nanorod continued to increase with escalating PEG_2k concentration, contrary to anticipated results. Subsequent investigation revealed a complex reaction between PEG_2k and Fe³⁺, wherein excessive PEG_2k concentration promoted nanorod elongation by forming complexes with Fe³⁺. Consequently, 0.20 g/L of PEG_2k concentration was identified as the optimal preparation condition, yielding nanorods with the average length of about 196 nm and average diameter of about 55 nm.

Fig. 3.

SEM morphologies A–H of β-FeOOH NRs fabricated at hydrolytic temperature of 80 °C for 2.0 h with PEG_2k of 0.05 g/L, 0.10 g/L, 0.20 g/L, 0.30 g/L, 0.40 g/L, 0.50 g/L, 0.60 g/L, 0.70 g/L and ferric trichloride of 0.20 M, and their corresponding average lengthes and diameters I based on sample quantity of n ≥ 100

Realizing that temperature was also a significant factor in crystal formation, therefore, the hydrolysis temperature was investigated, the SEM morphologies of β-FeOOH NRs fabricated at 75 °C, 80 °C, 85 °C, 90 °C, 95 °C for 2.0 h with PEG_2k of 0.20 g/L and ferric trichloride of 0.20 M, and their corresponding average length and diameter were revealed in Fig. 4. At 70 °C and below, the solid precipitation in the reaction system was basically invisible to the naked eye, and only a small amount of precipitation was obtained after high-speed centrifugation, so the temperature was continued to rise for the experiment. At 75 °C, the nanorods had the length and diameter of about 321 nm and 78 nm, far exceeding the expected size. With the enhancement of hydrolytic temperature, the movement and diffusion ability of atoms (especially grain boundary atoms) continued to increase, and the absorption rate between grains increased, this growth of grains could be completed in a very short time. So it was an inevitable phenomenon that the grain grew with the increase in temperature. At 80 °C, however, the length of the resulting nanorods dropped to about 200 nm, possibly because the crystals had reached the critical deformation zone. The critical deformation zone belonged to a small deformation range. Because of its small amount of deformation, only local areas of the metal were affected by deformation. During recrystallization, these deformed local areas would produce recrystallized cores, and because the number of cores produced was small, these few cores would continue to grow until they came into contact with each other, resulting in coarse grains. When deformation exceeded the critical threshold, substantial plastic deformation occurred within the metal, driven by high distortion energy. Consequently, recrystallization initiated the formation of multiple recrystallized cores simultaneously, which then coalesce slightly, resulting in finer grains post-recrystallization. As temperature rose, the time required to reach the critical deformation zone decreases, potentially enabling continued growth of these finer grains into larger particles. Additionally, the increase of temperature promoted the production of PEG_2k and Fe³⁺ complex products, further contributing to the gradual elongation of nanorods.

Fig. 4.

SEM morphologies A–E of β-FeOOH NRs fabricated at hydrolytic temperature of 75 °C, 80 °C, 85 °C, 90 °C, 95 °C for 2.0 h with PEG_2k of 0.20 g/L and ferric trichloride of 0.20 M, and their corresponding average lengthes and diameters F based on sample quantity of n ≥ 100

Finally, the time required for the precursor β-FeOOH formation process was verified by screening (Fig. 5). The relatively short water bath time resulted in the larger size of nanorods due to the presence of PEG_2k complexation and whether the nanorods reached the critical deformation zone. With the increase of the water bath time, the size of the nanorods decreased sharply due to the above-mentioned distortion energy which caused the deformation to be greater than the critical deformation degree. As the time of the water bath continued to increase, these tiny crystals continued to grow, so the size of the nanorods continued to increase until the second critical deformation region was reached.

Fig. 5.

SEM morphologies A–F of β-FeOOH NRs fabricated at hydrolytic temperature of 80 °C for 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h with PEG_2k of 0.20 g/L and ferric trichloride of 0.20 M, and their corresponding average lengthes and diameters G based on sample quantity of n ≥ 100

In summary, the best conditions for the fabrication of the β-FeOOH NRs were 0.02 M Fe³⁺, 0.20 g/L PEG_2k, hydrolytic temperature of 80 °C, and hydrolytic duration of 2.0 h.

Characteristics of α-Fe₂O₃/Fe₃O₄ MHNRs

The morphology, size, composition, and magnetic properties of the fabricated α-Fe₂O₃/Fe₃O₄ MHNMs were shown in Fig. 6. The TEM image (Fig. 6A) illustrated the overall morphology of α-Fe₂O₃/Fe₃O₄ MHNRs as spindle-shaped nanorods, with a measured mean longitudinal length of 229 nm and a mean transverse diameter of 55 nm. The phase composition and crystal structure of α-Fe₂O₃/Fe₃O₄ MHNRs were characterized by XRD technique (Fig. 6B). By conducting precise measurements and comparisons of the diffraction rings, the rings corresponded to the crystal planes represented by the XRD diffraction peaks at 24.1°, 30.1°, 33.2°, 35.4°, 40.9°, 43.1°, 49.5°, 54.1°, 56.9°, 62.4° and 73.9° respectively. The observed diffraction peaks were indexed as (012), (220), (104), (311), (113), (400), (024), (116), (511), (214), and (533), respectively. The most diffraction peaks corresponded to the standard PDF card of α-Fe₂O₃ (JCPDS. 00-033-0664), it was not hard to find that the diffracted intensity ratio for the peaks at 33.2° and 35.4° in the standard α-Fe₂O₃ PDF card was about 1.4085:1; however, the diffracted intensity ratio for the peaks of the prepared sample at 33.2° and 35.4° was 0.8495:1, obviously, the diffracted intensity at 35.4° was enhanced, the reason for which was that the diffracted intensity at 35.4° of Fe₃O₄ (JCPDS. 00-019-0629) advanced the diffracted intensity of the prepared sample, which also confirmed the successful preparation of α-Fe₂O₃/Fe₃O₄ MHNRs [20]. Figure 6C showed the hysteresis loops of α-Fe₂O₃/Fe₃O₄ MHNRs, which revealed the peculiarity of superpara magnetism, and their saturation magnetization achieved 81.3 emu·g^− 1.

Fig. 6.

TEM image (A), XRD spectrum (B), and the hysteresis loops (C) of α-Fe₂O₃/Fe₃O₄ MHNRs prepared at 450 °C for 2.0 h with the ratio of 3:1 for PEG_2k and β-FeOOH

To further verify the successful preparation of α-Fe₂O₃/Fe₃O₄ MHNRs, XPS analysis was carried out to confirm the element composition and chemical state of the product as Fig. 7. The comprehensive spectrum was displayed in Fig. 7A, the states of Fe and O elements were marked. In the C 1s spectrum (Fig. 7B), the C–O and O–C=O peaks appeared at 286.3 eV and 288.5 eV, respectively. Which corresponded to the presence of C–O/O–C=O peak at 530.77 eV in the O 1s spectrum (Fig. 7D) [21]. In the XPS spectrum of Fe 2p (Fig. 7C), the distinct peaks at 710.4 eV and 724.0 eV respectively corresponding to Fe 2p_3/2 and Fe 2p_1/2. The peaks at 712.2 eV and 726.2 eV indicated the existence of Fe³⁺ [22]; while, the peaks at 710.2 eV and 723.8 eV certified the existence of Fe²⁺ [23]. Furthermore, the satellite peaks resulting from energy dissipation caused by electron transitions in the valence band were observed at 718.4 eV and 732.6 eV. These characteristics collectively validated again the successful preparation of α-Fe₂O₃/Fe₃O₄ MHNRs.

Fig. 7.

XPS survey (A), C 1s (B), Fe 2p (C), and O 1s (D) core-level spectra of α-Fe₂O₃/Fe₃O₄ MHNRs

Effects of different preparation conditions on α-Fe₂O₃/Fe₃O₄ MHNRs

Figure 8 presented the XRD spectra and hysteresis loops of α-Fe₂O₃/Fe₃O₄ MHNRs prepared at various calcination temperatures for different calcination times with different ratios of PEG-2000 to β-FeOOH. The XRD spectra and hysteresis loops of α-Fe₂O₃/Fe₃O₄ MHNRs prepared at calcination temperature of 400 °C for 2.0 h with different ratios of PEG_2k and β-FeOOH were displayed in Fig. 8A and D. With the ratio of PEG_2k and β-FeOOH increasing from 2:1 to 3:1, the diffracted intensity ratio for the peaks at 33.2° and 35.4° obviously increased, and the saturation magnetization (Ms) increased from 57.8 to 122.0 emu/g; with the continuous increase of the ratio, the diffracted intensity ratio for the peaks at 33.2° and 35.4° maintained minor changes, while, Ms also maintained minor changes of 125.0–128.8 emu/g, and as the the ratio of PEG_2k and β-FeOOH achieved 6:1, Ms reached the maximum value of 128.8 emu/g. However, the magnetic strength did not continue to increase with the further addition of PEG_2k; instead, it decreased. This had to mention this reduction mechanism. As the temperature rose, PEG_2k melted and came into contact with β-FeOOH, subsequently losing hydrogen and oxygen elements to become a carbon source in the system. Finally, an oxidation-reduction reaction occurred during high-temperature calcination, resulting in the formation of α-Fe₂O₃/Fe₃O₄ MHNRs. When the proportion of PEG_2k became too high, the 2.0 h calcination at 400 °C was insufficient to allow a complete reaction of the carbon source, leading to carbon dopant in the product, greatly affecting the magnetic properties of the sample. Considering the continuous increase in the ratio of the reducing agent, increasing the calcination time and temperature might yield samples with better magnetic properties. However, at a reducing agent to β-FeOOH ratio of 3:1, α-Fe₂O₃/Fe₃O₄ MHNRs with a magnetic strength of 122.0 emu/g could already meet the performance requirements for magnetic targeting. Furthermore, doubling the amount of PEG_2k not only resulted in a modest improvement of only 5.49 emu/g but also led to an increase in particle size. Therefore, a reducing agent to β-FeOOH ratio of 3:1 was the most economical and optimal calcination scheme.

Fig. 8.

XRD patterns A–C and the hysteresis loops D–F of α-Fe₂O₃/Fe₃O₄ MHNRs prepared at various calcination temperatures for different calcination times with different ratios of PEG-2000 to β-FeOOH

The XRD spectra and hysteresis loops of the α-Fe₂O₃/Fe₃O₄ MHNRs prepared at various calcination temperature for 2.0 h with the ratio of 3:1 for PEG_2k and β-FeOOH were revealed in Fig. 8B and E. As the calcination temperature rose, there was a gradual increase in the diffraction peaks, leading to improved crystallinity, which revealed the increase in the grain size of α-Fe₂O₃/Fe₃O₄ MHNRs. Additionally, a noticeable rise in the proportion of Fe₂O₃ component in the α-Fe₂O₃/Fe₃O₄ MHNRs was observed with the rise of the calcination temperature. This phenomenon could be attributed to the heightened consumption of carbon sources at higher calcination temperatures, facilitating the oxidation of α-Fe₂O₃/Fe₃O₄ NRs to the desired oxidation state. The trend of XRD pattern (Fig. 8B) suggested a potential inverse relationship between the calcination temperature and Ms, indicating that higher calcination temperatures might result in the diminishment of magnetic characteristics. This inference was supported by the VSM curves depicted in Fig. 8E, where an incremental rise in calcination temperature correlated with a gradual decline in magnetic properties. Considering the pivotal role of heterogeneous structure and magnetic property in influencing agglomeration and the effectiveness of α-Fe₂O₃/Fe₃O₄ NRs for biomedical applications, the calcination temperature of 450 °C was determined as optimal.

Certainly, the calcination time also played a significant role in shaping the formation of α-Fe₂O₃/Fe₃O₄ MHNRs. The XRD spectra and hysteresis loops of α-Fe₂O₃/Fe₃O₄ MHNRs prepared at 450 °C for various calcination times with the ratio of 3:1 for PEG_2k and β-FeOOH were depicted in Fig. 8C and F. With the prolongation of calcination time, there was a gradual increase in the proportion of Fe₂O₃ component. In theory, this increment should lead to a gradual reduction in magnetic property. However, the VSM curves revealed a nuanced trend of initially increase and then decrease of magnetic properties with the maximum value of 81.3 emu/g. This phenomenon could be attributed to the delayed or incomplete redox reaction of the carbon source, resulting in the incorporation of residual carbon sources. Consequently, this impacted the magnetic properties of α-Fe₂O₃/Fe₃O₄ MHNRs. In summary, the calcination time of 2.0 h was deemed optimal based on these observations. Acooding to above the analysises, the related preparation conditions and parameters for α-Fe₂O₃/Fe₃O₄ MHNRs were summarized as Table 1.

Table 1.

The related preparation conditions and parameters for α-Fe₂O₃/Fe₃O₄ MHNRs

Calcination temperature (°C)	Calcination time (h)	The ratio of PEG-2000 to β-FeOOH	Ms (emu/g)
400	2.0	2:1	57.8
400	2.0	3:1	122.0
400	2.0	4:1	128.7
400	2.0	5:1	125.0
400	2.0	6:1	128.8
400	2.0	7:1	125.8
350	2.0	3:1	127.5
450	2.0	3:1	100.0
500	2.0	3:1	118.1
450	0.5	3:1	70.6
450	1.0	3:1	73.2
450	2.0	3:1	81.3
450	3.0	3:1	61.4
450	4.0	3:1	59.8
450	5.0	3:1	62.2

Conclusions

The paper presented a comprehensive research on the preparation and characterization ofα-Fe₂O₃/Fe₃O₄ MHNRs using polyethylene glycol 2000 (PEG_2k) as a growth inhibitor through the hydrolysis-calcination process. Firstly, Fe³⁺ concentration, PEG_2k concentration, hydrolytic temperature, and hydrolytic duration for the fabrication of β-FeOOH NRs were optimized as 0.02 M, 0.20 g/L, 80 °C, and 2.0 h, respectively; and the β-FeOOH NRs with the average length and diameter of approximately 199 nm and 55 nm were obtained. Secondely, the ratios of PEG-2000 to β-FeOOH, calcination temperatures, and calcination time for the preparation of α-Fe₂O₃/Fe₃O₄ MHNRs were optimized as 3:1, 450 °C, and 2.0 h, respectively, and their average length and diameter were 229 nm and 55 nm, and the saturation magnetization achieved 81.3 emu/g.

This research highlighted the importance of optimizing synthesis conditions to achieve desired properties, which could be extended to other magnetic nanomaterials for various applications. The successful preparation of these nanorods with controlled magnetism opened up new possibilities for the development of advanced biomedical technologies and contributes to the growing field of magnetic nanomaterials.

Author contributions

ZP: conducted material preparation, data acquisition, analysis and interpretation of data, and wrote the first draft of the paper. WL, ZZ, RC, and TW conducted material characterization, analysis and interpretation of data. ZL made contributions to the conception or design of the research and experiment, guide the experimental operation, review, revise and edit the article, and supervise the experimental research.

Funding

The authors did not receive support from any organization for the submitted work.

Data availability

The raw/processed data required to reproduce these findings can be requested from the corresponding author.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

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